Since the 9th century the musical tradition of the Mediterranean Sea was based in great part on the oud. The heart of oud music are the maqams, which are scales or 'composition rules’, roughly equivalent to Western keys.

The oud is a very popular and widespread instrument. It usually has five strings tuned to G', A', D, G, C, but six strings have become common. It comes in various shapes. The Aleppan oud (‘ud halabi) is the longest and most slender, famous for its perfect octave harmonics. The Damascene oud (‘ud shami) has a larger soundbox. The Egyptian oud (‘ud masri) has a weak upper octave. The Turkish oud (“ud turki) is the shortest of this family.

The oud's body has a staved, bowl-like back which allows the oud to resonate and have a complex tone. It has one to three sound-holes, which can be richly ornamented by a rosette design or wood inlay. The pegbox is bent back at a 45-90° angle from the neck of the instrument.

Syrian manufacturers test the rigidity of the different lute boxes by putting them on the ground and standing on them.

The oud is the most important chordophone of urban and classical Arab music. It is known as amir altarab, or "the prince of enchantment." It is the favorite instrument among theorists, composers as well as amateur performers.

Between the eighth and tenth centuries, the oud had only four strings; a fifth was added by the Andalusian musician Ziryab, and a sixth later on in the fifteenth century.

The oud made his way to Europe in the 8th century via Spain, from where it developed into the guitar.


References:
al-hakawati http://al-hakawati.net/Art/ArtDetails/61/العود,
The New Grove Dictionary of Music and Musicians. Second edition, 2001. v 24, p 855., http://www.belly-dance.org/oud.html